Recent advances in digital information processing have made a wide range of services and functions available for delivering content to consumers at their premises. These services and functions include digital programming (movies, etc.), digital video-on-demand (VOD), personal video recorder (PVR), Internet Protocol television (IPTV) and digital media playback and recording. These services are typically provided by multiple vendors including e.g., cable service providers (e.g., MSOs), satellite television network providers, cellular service providers (CSPs) and so on.
Conditional access systems are well known and widely used in conjunction with various ones of the aforementioned content delivery services. Such systems provide secure transmission of a content stream to a digital receiver contained, for example, in a set-top box or a mobile terminal supporting content delivery services. To protect the content from unauthorized viewing, the data packets in the streams are scrambled (encrypted) with a randomly generated encryption key commonly referred to as a control word. In order to increase the security of the streams, the control words are changed periodically.
In order to descramble the scrambled data packets in the transport stream, the receiver must be informed about the current value of the control word. For the secure transmission of the control words, they are encrypted and sent in so-called entitlement control messages (ECMs) to the receiver. In order to process the ECMs, entitlement management messages (EMMs) transmit and manage the keys needed to decrypt ECMs. The ECM and EMM information streams are sent to the receiver in order to allow the receiver to decrypt EMMs, the ECMs and to descramble the content to which the subscriber is entitled.
The Digital Video Broadcast (DVB) SimulCrypt standard provides a common way for conditional access providers to interface with a scrambler (or encrypter) in order to receive the control words and synchronize the distribution of ECMs. The interface allows content to be secured by multiple Conditional Access (CA) providers since they each receive the same control word. This approach is called “key sharing” and the full system is described in the European Telecommunications Standards Institute (ETSI) TS 103 197 V1.3.1 (02-06) TM2117r3 Technical Specification for “Digital Video Broadcasting (DVB); Head-end implementation of DVB SimulCrypt”. DVB SimulCrypt is often cited as an alternative to Selective Multiple Encryption in situations where the CA providers are “cooperating” through key sharing.
In the SimulCrypt protocol, a standardized SimulCrypt synchronizer (SCS) is utilized with an entitlement control message generator (ECMG) interface to allow multiple conditional access systems to operate in parallel, each generating its own ECMs.